<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    @page {
      size: 1200px 600px;
    }
    :root {
      column-count: 4;
    }
    div {
      border: solid 1px;
      margin: 3px;
      padding: 3px;
    }
    div::nth-fragment(3) div {
      color: blue;
    }
    .break {
      display: block;
      break-after: column;
    }
  </style>
</head>
<body>
<div class="a">
  <div class="b">
    body > div::nth-fragment(1) > div::nth-fragment(1) <br/>
    this color should be black.
    <span class="break"></span>
    body > div::nth-fragment(2) > div::nth-fragment(2) <br/>
    this color should be black.
  </div>
  <div class="b">
    body > div::nth-fragment(2) > div::nth-fragment(1) <br/>
    this color should be black.
    <span class="break"></span>
    body > div::nth-fragment(3) > div::nth-fragment(2) <br/>
    this color should be blue.
    <span class="break"></span>
    body > div::nth-fragment(4) > div::nth-fragment(3) <br/>
    this color should be black.
  </div>
</div>
</body>
</html>
